1. Field of the Invention
The present invention relates to a double-acting hydraulic pressure intensifier with a supply connection, a return connection, a high-pressure connection, an intensifier piston assembly comprising a low-pressure piston in a low-pressure cylinder and two high-pressure pistons connected to the low-pressure piston each in a high-pressure cylinder, and with a switching valve assembly comprising a displaceable, hydraulically controlled valve element which on its two opposite sides in the direction of displacement comprises control pressure chambers with pressure application areas of different size, namely a first control pressure chamber with a smaller pressure application area and a second control pressure chamber with a larger pressure application area.
2. Description of the Related Art
A double-acting hydraulic pressure intensifier of this kind is known from U.S. Pat. No. 4,659,294. The switching valve comprises a valve slide which can be displaced to and fro in a housing under the action of pressures which act on its two end faces. The pressures are equal here. The forces required to move the valve slide are applied by the fact that the pressures act on pressure application areas of different size. The valve slide controls the delivery of fluid to the low-pressure cylinder, this being alternately to one or the other side of the low-pressure piston. In the high-pressure cylinders is then generated a pressure which corresponds to the pressure at the supply connection multiplied by the ratio of the working areas of low-pressure piston and high-pressure piston.
A further double-acting hydraulic pressure intensifier is known from U.S. Pat. No. 2,508,298. Here, even two low-pressure pistons with two high-pressure pistons which move in opposite directions are provided. Each low-pressure piston is controlled by a switching valve, wherein the two switching valves operate in dependence upon each other.
Double-acting hydraulic pressure intensifiers of this kind have basically been tried and tested. They are capable of raising to a higher pressure the fluid which is at the supply connection at a lower pressure, wherein naturally the fluid quantity which is then available at the higher pressure is smaller.
However, the following problem often arises during operation: when the fits are very close, in particular in the case of the switching valve, high friction losses arise. The pressure intensifier can then operate only at a relatively low working frequency, which reduces the fluid quantity available at higher pressure. If on the other hand greater tolerances are provided, then the switching valve and hence also the low-pressure piston can of course move to and fro more rapidly. But in return the leaks at the switching valve are correspondingly greater. This in turn results in the valve element of the switching valve under certain circumstances remaining not long enough in positions which are necessary for the low-pressure piston to perform a sufficiently large stroke of movement. In such cases it can happen that the pressure intensifier catches, that is, stops working.